JP7237709B2 - Developing rollers, process cartridges and image forming apparatuses - Google Patents

Description

The present invention relates to a developing roller, process cartridge and image forming apparatus.

2. Description of the Related Art In recent years, image forming apparatuses such as copiers and optical printers are becoming smaller and more energy efficient. One method for miniaturizing an image forming apparatus is to reduce the diameter of each member such as a developing roller and a toner supply roller. Also, as one of the methods for saving energy in the image forming apparatus, reduction in torque during rotation and rubbing of each member (reduction of penetration amount of each member and reduction in peripheral speed difference) can be cited. However, if the diameters of the developing roller and the toner supply roller are reduced, the penetration amount of each member is reduced, and the rotational torque is reduced by reducing the peripheral speed difference, the amount of the toner layer formed on the developing roller becomes insufficient. A uniform image may not be obtained.

In Patent Document 1, in order to improve the toner conveying force of a developing member, a part of insulating particles dispersed in a conductive elastomer is exposed, and the toner is electrically attracted to the charged insulating particles. A developer roller is disclosed that can transport toner through the roller.

JP-A-4-88381

In the developing roller described in Patent Document 1, an insulating portion made of insulating particles exposed on the surface is charged, and a local potential difference is generated between the charged insulating portion and the non-charged conductive portion. When there is a local potential difference, an electric field gradient is generated along with this potential difference. When an object is present in the electric field gradient, the force (gradient force) generated by this electric field gradient provides excellent toner conveying power.

On the other hand, in recent years, there has been a demand for image forming apparatuses to achieve higher image quality as well as lower torque during rubbing. According to the studies of the present inventors, it has been found that, in the case of the developing roller having the insulating portion, the electric potential generated by the charging of the insulating portion fluctuates, easily causing the image density to change.
In other words, the potential of the insulating portion changes under the influence of the potential of the photoreceptor during image formation and changes in the state of the toner and the insulating portion due to repeated image formation. Since the development electric field for image formation changes with the change in the potential of the insulating portion, the change in image density becomes conspicuous. Therefore, suppression of the influence of the potential change of the insulating portion is a problem to be solved in order to perform more stable image formation.

In order to suppress the image density change due to the change in the potential of the insulating portion, for example, it is conceivable to lower the electric resistance value of the insulating portion. However, in this case, the amount of charge in the insulating portion is insufficient, and the toner conveying force tends to decrease in some cases.

One aspect of the present invention is directed to providing a developing roller capable of achieving both high toner conveying power and suppression of image density change. Another aspect of the present invention is directed to providing a process cartridge that contributes to the formation of high-quality electrophotographic images. Furthermore, another aspect of the present invention is directed to providing an electrophotographic apparatus capable of forming a high-quality electrophotographic image.

According to one aspect of the invention,
A developing roller having a conductive substrate and a coating layer on the conductive substrate,
The coating layer has a matrix containing a binder resin and conductive particles dispersed in the matrix,
A 90 μm × 90 μm square measurement area on the outer surface of the coating layer was measured under an environment of a temperature of 23 ° C. and a relative humidity of 50% using a scanning probe microscope with a triangular pyramid tip, a tip curvature radius of 25 nm, and a spring constant of is 42 N/m, and the current value is measured by scanning in a tapping mode while applying a potential difference of 10 V in the thickness direction of the coating layer, the arithmetic average value of the current value is 300 pA or less. , the standard deviation of the current value is 0.1 times or less of the current value,
The outer surface of the coating layer was subjected to a temperature of 23° C. and a relative humidity of 50% using a corona charger, and a potential difference of +8 kV was applied to the coating layer surface. 1 mm, and electrified while scanning at a speed of 400 mm/sec in the longitudinal direction of the developing roller. In an environment with a relative humidity of 50%, the potential is measured while the distance between the coating layer surface and the cantilever of the surface potential measuring device is 5 μm, and the standard deviation of the obtained potential is 3.0 V or more. hand,
A stainless steel roller having a diameter of 30 mm and a width of 10 mm was placed in an environment with a temperature of 23° C. and a relative humidity of 50% so that the axial direction of the stainless steel roller and the axial direction of the developing roller were perpendicular to each other. The circumferential surface of the manufacturing roller and the circumferential surface of the developing roller are opposed to each other, and the stainless steel roller is brought into contact with the developing roller surface with a load of 0.10 MPa. A potential difference of 10 V was applied between the roller and the conductive substrate, and the stainless steel roller and the conductive substrate were separated while rolling the stainless steel roller in the axial direction of the developing roller at a speed of 50 mm/sec. When the current value is measured at 36 points in the circumferential direction of the developing roller, the arithmetic mean value of the volume resistivity obtained from the measured current value is 10 ¹⁰ Ω cm or less, A developer roller is provided wherein the standard deviation is greater than or equal to 1 times the arithmetic mean value of the volume resistivity.

According to another aspect of the present invention, there is provided a process cartridge detachably attached to a main body of an electrophotographic apparatus, the process cartridge including the developing roller described above.

According to still another aspect of the present invention, there is provided an electrophotographic image forming apparatus having a photoreceptor and a developing roller for supplying developer to an electrostatic latent image formed on the photoreceptor, An electrophotographic image forming apparatus is provided, wherein the developing roller is the above developing roller.

1 is a cross-sectional view showing an embodiment of a developing roller according to this aspect; FIG. 1 is a cross-sectional view showing one embodiment of a coating layer according to this aspect; FIG. 1 is a schematic configuration diagram showing an embodiment of a process cartridge according to this aspect; FIG. 1 is a schematic configuration diagram showing an embodiment of an image forming apparatus according to this aspect; FIG. 1 is a schematic configuration diagram of a device used for current value measurement during pressing in an example. FIG.

A developing roller according to an aspect of the present invention has a conductive substrate and a coating layer on the conductive substrate, and the coating layer comprises a matrix containing a binder resin and conductive particles dispersed in the matrix. and having the following three properties:

characteristic 1;
A 90 μm × 90 μm square measurement area on the outer surface of the coating layer was measured under an environment of a temperature of 23 ° C. and a relative humidity of 50% using a scanning probe microscope with a triangular pyramid tip, a tip curvature radius of 25 nm, and a spring constant of is 42 N/m, and the current value is measured by scanning in tapping mode while applying a potential difference of 10 V in the thickness direction of the coating layer, the arithmetic average value of the current value is 300 pA or less, standard The deviation is 0.1 times or less of the current value.

Characteristic 2;
The outer surface of the coating layer was subjected to a temperature of 23° C. and a relative humidity of 50% using a corona charger, and a potential difference of +8 kV was applied to the coating layer surface. 1 mm, and electrified while scanning at a speed of 400 mm/sec in the longitudinal direction of the developing roller. , The standard deviation of the obtained potential is 3.0 V or more when the potential is measured while the distance between the coating layer surface and the cantilever of the surface potential measuring device is 5 μm in an environment of 50% relative humidity.

characteristic 3;
A stainless steel roller having a diameter of 30 mm and a width of 10 mm was placed in an environment with a temperature of 23° C. and a relative humidity of 50% so that the axial direction of the stainless steel roller and the axial direction of the developing roller were perpendicular to each other. The circumferential surface of the manufacturing roller and the circumferential surface of the developing roller are opposed to each other, and the stainless steel roller is brought into contact with the developing roller surface with a load of 0.10 MPa. A potential difference of 10 V was applied between the roller and the conductive substrate, and the stainless steel roller and the conductive substrate were separated while rolling the stainless steel roller in the axial direction of the developing roller at a speed of 50 mm/sec. When the current value is measured at 36 points in the circumferential direction of the developing roller, the arithmetic mean value of the volume resistivity obtained from the measured current value is 10 ¹⁰ Ω cm or less, The standard deviation is 1 or more times the arithmetic mean value of the volume resistivity.

The inventors of the present invention have found that a developing roller that satisfies the above properties 1 to 3 can achieve both suppression of image density change and high toner conveying power at a high level. The inventors presume that this is due to the following two reasons.

The first reason is that the developing roller according to this aspect exhibits a gradient force on the surface of the coating layer.
Satisfying the characteristic 1 means that substantially the entire surface of the coating layer of the developing roller according to this aspect exhibits insulation over the entire surface from when no pressure is applied to when the pressure is extremely light. In the present invention, when the arithmetic average value of the current values is 300 pA or less, the insulating properties are easily obtained. Further, when the standard deviation is 0.1 times or less of the current value, partial charge leakage sites are suppressed.
Satisfying property 2 means that a local potential difference is generated when the coating layer is charged. In the present invention, when the standard deviation of the potential is 3.0 V or more, an excellent toner transport amount can be obtained. The standard deviation of the potential is more preferably 4.0 V or more, and even more preferably 5.0 V or more. When a roller having such a coating layer is used as a developing roller, the surface of the coating layer is charged by friction with toner or the like. Furthermore, along with this, a local potential difference is generated on the coating layer surface. It is presumed that this local potential difference produces a gradient force, resulting in an excellent toner conveying force.

The second reason is that the developing roller according to this aspect exhibits conductivity when pressed.
Satisfying the characteristic 3 means that the coating layer, which is insulative over the entire surface when no pressure is applied to a very light pressure, exhibits conductivity when the pressure is applied.
When used as a developing roller of the contact development method, the coating layer is pressed by the photoreceptor at the developing position where the photoreceptor and the developing roller arranged opposite to the photoreceptor come into contact. At this time, in order to stabilize the contact state between the developing roller and the photoreceptor, a contact pressure of about 0.10 MPa is applied between the developing roller and the photoreceptor.
Characteristic 3 means that the developing roller according to this aspect develops electrical conductivity under a pressure that is approximately the same as the pressure applied between the developing roller and the photoreceptor.
As a result, the developing roller exhibits electrical conductivity at the developing position, so that the charge on the surface of the coating layer that has been charged is canceled, and an appropriate developing electric field can always be formed at the developing position. In the present invention, when the arithmetic mean value of the volume resistivity is 10 ¹⁰ Ω·cm or less, the change in the development electric field at the development position can be suppressed. In addition, when the standard deviation is 1 or more times the arithmetic mean value of the volume resistivity, the coating layer can be more uniformly conductive when pressed. Therefore, even if the potential of the surface of the coating layer, which is insulative when not pressed, changes due to changes in the state of the toner, etc. due to repeated image formation, and changes in the environment, changes in the development electric field can be suppressed, and changes in image density can be suppressed. I'm assuming it can.

In the developing roller according to this aspect, the surface of the coating layer is insulating when not pressed (characteristic 1), and when the surface of the coating layer is charged, a local potential difference occurs on the surface (characteristic 2), In addition, it is a developing roller in which the surface of the coating layer becomes conductive when pressed (characteristic 3). It is presumed that due to these characteristics, it is possible to achieve both excellent toner conveying ability and suppression of image density change.

FIG. 1 shows an embodiment of the developing roller according to this aspect. The developer roller 1 shown in FIG. 1 has a conductive substrate 2 and a coating layer 3 on the conductive substrate 2 . Further, the developing roller according to this aspect may have one or more layers such as the conductive elastic layer 4 between the substrate and the coating layer, like the developing roller 1 shown in FIG. Furthermore, FIG. 2 shows an enlarged view of the cross section of the coating layer 3 in FIG.

The developing roller according to this aspect more preferably expresses the above characteristics 1 to 3 by having each configuration of the following requirements i) to ix).

Requirement i) The potential decay time constant of the matrix is 1.0 min or more in an environment with a temperature of 23° C. and a relative humidity of 50%;
Requirement ii) that the mode of the equivalent spherical diameter of the conductive particles is 3.0 μm or more and 20 μm or less;
Requirement iii) the ratio of the conductive particles to the total volume of the coating layer is 20% by volume or more and 45% by volume or less;
Requirement iv) that the layer thickness of the coating layer is 3.0 μm or more and 30 μm or less;
Requirement v) The arithmetic mean value of the number of conductive particles overlapping in the thickness direction of the coating layer is 3 or less;
Requirement vi) The nanoindenter hardness of the matrix on the surface of the coating layer is 0.1 N/mm ² or more and 3.0 N/mm ² or less in an environment with a temperature of 23 ° C. and a relative humidity of 50%;
Requirement viii) that the nanoindenter hardness on the conductive particles is 1.0 N/ ^mm2 or more and 10.0 N/ ^mm2 or less;
Requirement ix) that the nanoindenter hardness on the conductive particles is greater than the nanoindenter hardness of the matrix.

The mode of the spherical volume equivalent diameter of the conductive particles dispersed in the matrix is set to 3.0 μm or more, and the volume ratio of the conductive particles to the total volume of the coating layer is set to 45% by volume or less. By setting the potential decay time constant of the matrix to 1.0 min or more, the characteristic 1 can be exhibited more satisfactorily. The reason is inferred as follows.

Requirement i) means that the developing roller has an insulating property that enables the surface of the coating layer to be charged, which is necessary for manifesting the toner transporting force of the developing roller. This means that the matrix is insulating.
The mode value of the spherical volume equivalent diameter of the conductive particles described in the above requirement ii) is one to two orders of magnitude larger than that of a general electronic conductivity-imparting agent such as carbon black. Therefore, when the conductive particles are dispersed in the matrix, it is considered that the conductive particles are less likely to agglomerate or come close to each other due to rearrangement, and the conductive particles are less likely to be exposed to the surface or interface. For this reason, the conductive particles are added to the commonly used electronically conductive particles having a volume ratio of the conductive particles in the entire coating layer of 20% by volume or more and 45% by volume or less as described in the above requirement iii). In the case of the property-imparting agent, even when the coating layer is dispersed in the matrix in such an amount that it exhibits high conductivity, it is considered that the conductive paths are less likely to be formed.
For the reasons described above, it is presumed that the developing roller satisfying the requirements i) to iii) satisfactorily exhibits the characteristic 1 described above.

Further, by satisfying the above requirements ii) to v), the characteristic 2 can be exhibited more favorably. The reason is inferred as follows.

In FIG. 2, the thickness of the insulating layer at point A on the surface of the coating layer is t1. In addition, the layer thickness as the insulating layer at point B is t2-d, which is obtained by subtracting the particle diameter d of the conductive particles 6 from the film thickness t2 of the coating layer, and the layer thickness as the insulating layer of the coating layer is Local differences exist.
According to Coulomb's law, the surface potential V when there is a charge Q on an insulator is V=Q/(ε×S/a). Here, ε is the dielectric constant of the insulator, S is the area of the insulator, and a is the thickness of the insulator. This means that if there is a charge on the surface of an insulator, its surface potential is proportional to the thickness of the insulator.
That is, since the coating layer according to the present embodiment exhibits insulating properties when not pressed and has a local difference in layer thickness as an insulating layer, the surface of the coating layer is charged by rubbing with toner or the like. In this case, it is considered that a local potential difference is developed.

By satisfying the above requirements ii) and iii), the coating layer has a large local layer thickness difference as an insulating layer. This makes it easier to develop the local potential difference of characteristic 2 for developing excellent toner transport force, that is, gradient force.
Furthermore, by satisfying the requirement iii), the insulating property of the coating layer can be maintained when not pressed, and the matrix of a certain volume or more can be present, forming a local layer thickness difference as an insulating layer. This is preferable because it makes it easier to
Furthermore, by satisfying the requirement v), local differences in layer thickness are likely to be formed in the coating layer. It is presumed that this is because as a large number of the conductive particles overlap in the thickness direction of the coating layer, the thickness of the coating layer as an insulating layer is averaged and local differences become smaller. The arithmetic mean value of the number of the conductive particles overlapping in the thickness direction of the coating layer is the layer thickness of the coating layer, the mode of the spherical volume equivalent diameter of the conductive particles, and the total coating layer. It can be controlled by the volume ratio of the conductive particles.
As shown in FIG. 2, the thickness of the coating layer varies with t1 and t2 due to the presence of conductive particles. The arithmetic average value of the layer thickness measured at random is taken as the layer thickness of the coating layer.

Furthermore, by satisfying requirements ii) to iv) and requirements vi) to ix), the property 3 can be exhibited better. The reason for this is inferred as follows.

It is speculated that the nanoindenter hardness of the matrix is small, that is, the matrix is flexible, so that the matrix is easily deformed when the coating layer is pressed. Also, the nanoindenter hardness on the conductive particles strongly reflects the hardness of the conductive particles. The nanoindenter hardness on the conductive particles is large and the nanoindenter hardness of the matrix is higher, that is, the conductive particles are harder than the matrix, so that the coating layer is It is believed that deformation of the conductive particles is suppressed when the matrix is deformed by being pressed. When the coating layer is pressed under such conditions, the coating layer surface and the conductive particles, the adjacent conductive particles in the coating layer, and the conductive particles and the conductive substrate , are in close proximity and the coating layer is rendered conductive.
Further, it is considered that by setting the volume ratio of the conductive particles in the entire coating layer to 20% by volume or more, the approach via the conductive particles is likely to occur.

Furthermore, by satisfying requirements ii) and iv), it is possible to achieve both excellent toner conveying power and suppression of image density change.
That is, it is considered that by satisfying the requirement ii), the conductive region on the surface of the coating layer during pressing can be made fine. When using a general toner having an average particle diameter of about several μm for use in copiers and the like, if the mode of the spherical volume equivalent diameter of the conductive particles is 20 μm or less, conductivity is exhibited when pressed. It is presumed that the interval between the conductive particles becomes minute, and the change in image density can be suppressed. The fineness of this conductive region can be represented by the conductive point density at the time of pressing, which is calculated by the measuring method described later.
The conductive point density at the time of pressing is preferably 10/100 μm square or more because it is easy to suppress image density change, more preferably 15/100 μm square or more, further preferably 20/100 μm square or more. be.
Furthermore, by satisfying the requirement iv), when the mode of the spherical volume equivalent diameter of the conductive particles is 20 μm or less, the arithmetic mean value of the number of overlapping conductive particles in the thickness direction of the coating layer can be easily made small, and excellent toner conveying power can be easily obtained.

Hereinafter, the developing roller according to one aspect of the present invention will be described in detail.
[Development roller]
The developing roller has a conductive substrate and a coating layer as the outermost layer on the conductive substrate. Further, as shown in FIG. 1, the developing roller may have one or more layers such as a conductive elastic layer 4 between the conductive substrate 2 and the coating layer 3, if necessary.

<Substrate>
The substrate can be conductive and has the function of supporting the coating layer and the conductive elastic layer provided thereon. Examples of materials for the substrate include metals such as iron, copper, aluminum and nickel; alloys containing these metals such as stainless steel, duralumin, brass and bronze. These may be used alone or in combination of two or more. The surface of the substrate can be plated for the purpose of imparting scratch resistance to the extent that the conductivity is not impaired. Furthermore, a base made of resin whose surface is coated with a metal to make the surface conductive, or a base made of a conductive resin composition can also be used.

<Coating layer>
The coating layer includes a matrix containing a binder resin and conductive particles dispersed in the matrix.

When a layer such as a conductive elastic layer is provided between the substrate and the coating layer, the thickness of the coating layer is preferably 3.0 µm or more and 30 µm or less, more preferably 5.0 µm or more and 15 µm or less. If the thickness is 3.0 μm or more, as described above, it is easy to form a local layer thickness difference as an insulating layer on the surface of the coating layer. Since the arithmetic average value of the number of overlapping conductive particles in (1) can be easily reduced, an excellent toner conveying force can be easily obtained. In addition, the thickness of the coating layer is a value measured by a method described later.

The matrix contains a binder resin. Further, as shown in FIG. 2, the matrix 5 constitutes a region in the coating layer 3 that does not contain the conductive particles 6 and the insulating particles 7 described later.
When the matrix has a potential decay time constant of 1.0 min or more at a temperature of 23° C. and a relative humidity of 50%, the surface of the coating layer is easily charged, which is preferable from the viewpoint of improving toner transportability. It is more preferably 5.0 min or longer, and still more preferably 10 min or longer. The potential decay time constant is a value measured by a method described later.
When the volume resistivity of the matrix is 1.0×10 ¹³ Ω·cm or more, the potential decay time constant can be easily designed to be 1.0 min or more, which is preferable. The volume resistivity is preferably 1.0×10 ¹⁴ Ω·cm or more, more preferably 1.0×10 ¹⁵ Ω·cm or more, and even more preferably 1.0×10 ¹⁶ Ω·cm or more. Although the upper limit of the volume resistivity is not particularly limited, it can be, for example, 1.0×10 ¹⁹ Ω·cm or less. The volume resistivity of the matrix and the conductive particles described later can be measured, for example, with an atomic force microscope (AFM).

A specific measurement example of the volume resistivity is shown here.
An atomic force microscope (AFM) (trade name: Q-scope250, manufactured by Quesant) is used for measurement in the conductivity mode. The coating layer of the developing roller is cut into a sheet by using a microtome, and the conductive particles are cut out so that two opposite surfaces of the particles are exposed to obtain measurement pieces. Platinum vapor deposition is applied to one side of the cut measurement piece. Next, a DC power supply (trade name: 6614C, manufactured by Agilent) is connected to the platinum-deposited surface and 10 V is applied, and the free end of the cantilever is brought into contact with the other surface of the measurement piece, and the AFM body is passed through. Acquire a current image. The measurement conditions are shown below.
Measurement mode: contact
Cantilever: CSC17
Measurement range: 10nm x 10nm
Scan rate: 4Hz
Applied voltage 10V
Measurement environment: temperature 23°C, relative humidity 50%

This measurement is performed at 100 randomly selected locations. The volume resistivity is calculated from the average current value of the top 10 lowest current values among the measured locations, the average film thickness of the measurement piece, and the contact area of the cantilever. In the case of conductive particles whose surfaces are covered with a conductive substance, the volume resistivity is calculated from the average current value on the surface of the particles. The average film thickness of the measurement piece is obtained by observing a total of 10 cross sections of the cut measurement piece with an optical microscope or an electron microscope and taking the average value.

When the nanoindenter hardness of the matrix is 0.1 N/mm ² or more and 3.0 N/mm ² or less, the matrix can be sufficiently deformed when the coating layer is pressed, and the conductive particles are close to each other, thereby making the matrix conductive. is likely to occur, which is preferable. The nanoindenter hardness of the matrix can be controlled by the molecular structure of the binder resin and additives such as silica, which will be described later. The nanoindenter hardness can be measured by the method described later.

(binder resin)
The binder resin contained in the matrix is not particularly limited as long as it satisfies the preferred ranges of the volume resistivity and the nanoindenter hardness. Examples of such binder resins include polyurethane resins, polyamides, urea resins, polyimides, fluorine resins, phenolic resins, alkyd resins, silicone resins, polyesters, ethylene-propylene-diene copolymer rubber (EPDM), acrylonitrile-butadiene. Rubber (NBR), chloroprene rubber (CR), natural rubber (NR), isoprene rubber (IR), styrene-butadiene rubber (SBR), fluororubber, silicone rubber, hydrides of NBR, and the like. These can be used individually by 1 type or in combination of 2 or more types as needed. Among these, polyurethane resins are preferred because they are excellent in electrical insulation and flexibility, and have high abrasion resistance required for developing rollers. Examples of the polyurethane resin include ether-based polyurethane resins, ester-based polyurethane resins, acrylic-based polyurethane resins, polycarbonate-based polyurethane resins, and polyolefin-based polyurethane resins. Among these resins, polycarbonate-based polyurethane resins and polyolefin-based polyurethane resins are preferable because they tend to provide electrical insulation and flexibility.

式（５）中、ｌは１以上の整数を表し、１０以上の整数であることが好ましい。また、ｌの上限は特に限定されないが、例えば１００以下の整数であることができる。前記バインダー樹脂がこれらの構造を有することにより、高温高湿環境下に於いてもより高いトナー搬送力が得られ、且つ、低温低湿環境下に於いても画像濃度変化をより抑制できるという効果を奏する理由は未だ解明中であるが、本発明者らは以下のように推測している。 In particular, the binder resin has either or both of the structures represented by the following formulas (1) and (2) and either or both of the structures represented by the following formulas (3) and (4). and a structure represented by the following formula (5), a higher toner conveying force can be obtained even in a high-temperature and high-humidity environment, and image density changes even in a low-temperature and low-humidity environment. can be further suppressed, which is more preferable.

In formula (5), l represents an integer of 1 or more, preferably an integer of 10 or more. Also, the upper limit of l is not particularly limited, but it can be an integer of 100 or less, for example. When the binder resin has these structures, it is possible to obtain the effect of obtaining a higher toner conveying force even in a high-temperature and high-humidity environment and further suppressing the change in image density even in a low-temperature and low-humidity environment. Although the reason why it works is still being elucidated, the present inventors presume as follows.

The structures represented by formulas (1) to (4) have low polarity. Therefore, the hardness required for compressive deformation during pressing, that is, while softening to a nanoindenter hardness of 3.0 N / mm ² or less, the penetration of moisture in the environment into the resin is suppressed, and the high temperature It is considered that high electrical insulation can be maintained even in a high humidity environment.

Furthermore, the structures represented by formulas (3) and (4) have methyl groups in side chains. It is thought that this acts as a steric hindrance, thereby reducing the crystallinity of the binder resin and, in particular, suppressing an increase in the hardness of the binder resin under a low-temperature, low-humidity environment.

From the above, it can be concluded that the binder resin has one or both of the structures represented by the above formulas (1) and (2) and one of the structures represented by the above formulas (3) and (4). Alternatively, by having both structures and the structure represented by the above formula (5), both higher toner conveying power in a high temperature and high humidity environment and further suppression of image density change in a low temperature and low humidity environment are compatible. I'm assuming it can.

In order to introduce the structure represented by the above formula (1) into the binder resin, for example, polybutadiene polyol having the structure represented by the above formula (1) in the molecule can be used as a raw material. The weight average molecular weight of the polybutadiene polyol is preferably 500 or more and 5000 or less. Commercially available products include, for example, "G-1000", "G-2000", "G-3000" (all trade names, manufactured by Nippon Soda Co., Ltd.), "Poly ip" (trade name, Idemitsu Kosan Co., Ltd. ), “krasol LBH-2000” and “krasol LBH-P-3000” (both trade names, manufactured by Clay Valley). These may be used alone or in combination of two or more.

In order to introduce the structure represented by the formula (2) into the binder resin, for example, a hydrogenated polybutadiene polyol having the structure represented by the formula (2) in the molecule can be used as a raw material. The weight average molecular weight of the hydrogenated polybutadiene polyol is preferably 500 or more and 5000 or less. Commercially available products include, for example, "GI-1000", "GI-2000", "GI-3000" (all trade names, manufactured by Nippon Soda Co., Ltd.), "krasol HLBH-P 2000", "krasol HLBH- P 3000" (both trade names, manufactured by Clay Valley). These may be used alone or in combination of two or more.

In order to introduce the structure represented by the formula (3) into the binder resin, for example, a polyisoprene polyol having the structure represented by the formula (3) in the molecule can be used as a raw material. The weight average molecular weight of the polyisoprene polyol is preferably 500 or more and 5000 or less. Examples of commercially available products include "Poly ip" (trade name, manufactured by Idemitsu Kosan Co., Ltd.). These may be used alone or in combination of two or more.

In order to introduce the structure represented by the formula (4) into the binder resin, for example, a hydrogenated polyisoprene polyol having the structure represented by the formula (4) in the molecule can be used as a raw material. The weight average molecular weight of the hydrogenated polyisoprene polyol is preferably 500 or more and 5000 or less. Commercially available products include, for example, “Epol” (trade name, manufactured by Idemitsu Kosan Co., Ltd.). These may be used alone or in combination of two or more.

前記式（６）において、Ｌは１以上の整数を示す。Ｌの上限は特に限定されないが、例えば１００以下の整数であることができ、５０以下の整数であることが好ましい。前記ポリメリックＭＤＩを用いることで、イソシアネート基の余剰反応が抑制され、塗工液の安定性が向上する。また、あらかじめポリオールにより鎖延長したプレポリマーを用いてもよい。 In order to introduce the structure represented by the above formula (5) into the binder resin, as a raw material, for example, a polymeric MDI (polymethylene poly phenyl polyisocyanate) can be used.

In the formula (6), L represents an integer of 1 or more. Although the upper limit of L is not particularly limited, it can be, for example, an integer of 100 or less, preferably an integer of 50 or less. By using the polymeric MDI, excessive reaction of isocyanate groups is suppressed, and the stability of the coating liquid is improved. A prepolymer chain-extended with a polyol in advance may also be used.

The binder resin is, for example, a polyol containing either or both of a) and b) below and either or both of c) and d) below, and a polyisocyanate containing e) below. It can be obtained by reacting a mixture.
a) either or both of a compound comprising a structure represented by formula (1) and a prepolymer derived from a compound comprising a structure represented by formula (1);
b) either or both of a compound comprising a structure represented by formula (2) and a prepolymer derived from a compound comprising a structure represented by formula (2);
c) either or both of a compound comprising a structure represented by formula (3) and a prepolymer derived from a compound comprising a structure represented by formula (3);
d) either or both of a compound comprising a structure represented by formula (4) and a prepolymer derived from a compound comprising a structure represented by formula (4);
e) either or both of the compound of formula (6) and the prepolymer derived from the compound of formula (6).

The ratio of the number of moles of isocyanate to the number of moles of hydroxyl groups in the mixture, that is, the isocyanate index (NCO/OH) is preferably 1.1 or more and 5.0 or less. When the isocyanate index is within this range, residual unreacted components in the binder resin can be suppressed, and excellent insulation can be obtained in a high-temperature, high-humidity environment. Moreover, especially when the isocyanate index is 5.0 or less, the hardness of the matrix can be reduced in a low-temperature and low-humidity environment, and the matrix can be sufficiently deformed by pressing.

The structure of the binder resin can be confirmed by analysis using pyrolysis GC/MS (gas chromatograph-mass spectrometer), FT-IR (Fourier transform infrared spectrophotometer), NMR (nuclear magnetic resonance), or the like.

(Conductive particles)
The mode of the spherical volume equivalent diameter of the conductive particles is preferably 3.0 μm or more and 20 μm or less. When the average particle size is 3.0 μm or more, the insulating properties of the coating layer can be maintained when pressure is not applied. Moreover, it is easy to form a local layer thickness difference as an insulating layer of the covering layer. Further, when the mode of the sphere equivalent volume diameter is 20 μm or less, the electrically conductive region can be made finer when pressed, and the change in image density can be easily suppressed. More preferably, the mode of the equivalent spherical diameter of the conductive particles is 5.0 μm or more and 10 μm or less. The mode of the spherical volume equivalent diameter of the conductive particles is a value measured by the method described later.

The nanoindenter hardness on the conductive particles on the coating layer surface is preferably 1.0 N/mm ² or more and 10 N/mm ² or less. Further, it is preferable that the nanoindenter hardness on the conductive particles is higher than the nanoindenter hardness of the matrix. By setting the nanoindenter hardness of the projections derived from the conductive particles to be greater than the nanoindenter hardness of the matrix and 1.0 N/mm ² or more and 10.0 N/mm ² or less, as described above , is preferable because the conductivity of the coating layer can be easily obtained at the time of pressing. Further, by setting the nanoindenter hardness of the projections derived from the conductive particles to 10.0 N/mm ² or less, the coating layer is prevented from macroscopically having extremely high hardness, and stress to the toner is prevented. can be reduced.

The nanoindenter hardness on the conductive particles is more preferably 2.0 N/mm ² or more and 5.0 N/mm ² or less. The nanoindenter hardness on the conductive particles is preferably greater than the nanoindenter hardness of the matrix by 0.5 N/mm ² or more, more preferably by 1.0 N/mm ² or more. The nanoindenter hardness is a value measured by the method described later. The hardness of the nanoindenter on the conductive particles is affected by the hardness of the matrix, but the effect can be reduced by measuring by the method described later, and the correlation with the functionality of the present invention can be accurately estimated. can be done.

A ratio of the conductive particles to the total volume of the coating layer is preferably 20% by volume or more and 45% by volume or less. When the ratio is 20% by volume or more, the conductive particles can be brought close enough to each other to form an electrical flow path when pressed, thereby suppressing a change in image density, which is preferable. In addition, when the ratio is 45% by volume or less, it is possible to suppress the conductivity of the coating layer when not pressed, and the arithmetic average value of the number of overlapping conductive particles in the thickness direction of the coating layer is It is preferable because it is easy to reduce the size and easy to obtain an excellent toner conveying force. The ratio is more preferably 30% by volume or more and 40% by volume or less. In addition, the volume % of the conductive particles can be measured by the method described later.

It is preferable that the conductive particles have a volume resistivity of 1.0×10 ² Ω·cm or less, since an appropriate development electric field can be formed quickly when pressed. The volume resistivity is more preferably 1.0×10 ¹ Ω·cm or less, more preferably 1.0×10 ⁰ Ω·cm or less. Although the lower limit of the volume resistivity is not particularly limited, it can be, for example, 1.0×10 ⁻⁸ Ω·cm or more. The volume resistivity can be measured by the method described above.

It is preferable that the conductive particles have a spherical shape from the viewpoint of easily obtaining insulation when not pressed. Here, "spherical" means that the ratio of major axis/minor axis of the particles is 1.0 to 1.5. The major axis/minor axis ratio is preferably 1.0 to 1.2, more preferably 1.0 to 1.1. Incidentally, the major diameter and minor diameter of the conductive particles dispersed in the matrix can be calculated by observation with an ion beam processing apparatus (FIB-SEM) in the same manner as the measurement of the average particle diameter, which will be described later.

Examples of conductive particles having such properties include the following conductive particles. Metal particles such as Au powder and iron powder, resin particles coated with metal such as Ag on the surface, inorganic compound particles such as zinc oxide coated with metal on the surface, inorganic compound particles doped with metal, conductivity such as carbon black Resin particles with fine particles attached to the surface, inorganic compound particles with conductive fine particles attached to the surface, resin particles with conductive particles encapsulated therein, resin particles with ion conductive agents such as quaternary ammonium salts encapsulated therein, graphite particles , carbon particles. These conductive particles can be used singly or in combination of two or more as needed. Among these, carbon particles are preferable because they are excellent in conductivity and hardness. Furthermore, it is more preferable to use carbon particles obtained by carbonizing resin particles such as phenol resin by high-temperature treatment, because the toner conveying power is excellent. Carbon particles obtained by carbonizing resin particles by high-temperature treatment have a smooth surface, a small specific surface area, and a hydrophobic surface due to the high-temperature treatment. For this reason, the carbon particles are less likely to agglomerate or align in the matrix, and the carbon particles are more likely to be dispersed in an appropriately aligned state. Examples of such carbon particles include commercial products such as ICB0520 (trade name, manufactured by Nippon Carbon Co., Ltd.).

In particular, the binder resin has one or both of the structures represented by the above formulas (1) and (2) and one or both of the structures represented by the above formulas (3) and (4). and the structure represented by the above formula (5), and the conductive particles are carbon particles, it is possible to obtain excellent toner conveying power even in a high-temperature and high-humidity environment, preferable. This is probably because, in addition to the properties of the binder resin having the structure described above, when the binder resin and the carbon particles are used in combination, the undulation of the matrix during the formation of the coating layer is suppressed. When the undulation of the matrix during the formation of the coating layer is suppressed, the layer thickness difference as described above tends to occur as the insulating layer. It is believed that this makes the local potential difference on the surface of the coating layer steeper, resulting in an excellent toner conveying force. Although the reason why the matrix waviness is suppressed by the combination of the binder resin and the conductive particles is still being clarified, the present inventors presume as follows. That is, one or both of the structures represented by the above formulas (1) and (2), one or both of the structures represented by the above formulas (3) and (4), and the above formula It is presumed that the surface free energy of the binder resin having the structure shown in (5) and the carbon particles are close to each other, and the cohesive force between the carbon particles is reduced, thereby suppressing the waviness of the surface of the coating layer. ing.

Furthermore, when the specific circumference of the carbon particles obtained by the measurement method described later is 1.1 or less, it is possible to obtain a superior toner conveying force in a high-temperature and high-humidity environment, which is more preferable. It is believed that this is because when the binder resin and the carbon particles having the specific circumferential length are used in combination, the waviness of the matrix during the formation of the coating layer is further suppressed. Although the reason why the matrix waviness is suppressed by the combination of the binder resin and the conductive particles is still being clarified, the present inventors presume as follows. That is, when the specific perimeter is 1.05 or less, the surface of the conductive particles is very smooth, which reduces the interaction between the binder resin and the carbon particles and reduces the undulation of the surface of the coating layer. I'm assuming it's been suppressed.

(insulating particles)
The coating layer according to this aspect may further contain insulating particles in addition to the conductive particles.

The average particle size of the insulating particles is preferably 3.0 μm or more and 30 μm or less. When the average particle diameter is 3.0 μm or more, the thickness of the insulating layer is increased at the locations where the insulating particles are present, and the potential difference between the surrounding areas where the conductive particles are present is increased, A more excellent toner conveying force can be exhibited. Further, when the average particle diameter is 30 μm or less, the conductivity of the coating layer can be sufficiently maintained during pressing, and the change in image density can be easily suppressed. More preferably, the average particle size is 5.0 μm or more and 15 μm or less. The average particle size can be measured by the method described later.

When the volume resistivity of the insulating particles is 1.0×10 ¹⁰ Ω·cm or more, the potential difference between the surrounding area where the conductive particles are present is increased, resulting in a better toner transporting force. It is preferable because it becomes easy to express. More preferably, the volume resistivity is 1.0×10 ¹³ Ω·cm or more. Although the upper limit of the volume resistivity is not particularly limited, for example, it is preferably 1.0×10 ¹⁶ Ω·cm or less because it is easy to suppress the image density change. The volume resistivity can be measured by the method described above.

Examples of insulating particles having such properties include resin particles such as acrylic resins, urethane resins, fluororesins, polyester resins, polyether resins, and polycarbonate resins, and inorganic compound particles such as silica, alumina, and silicon carbide. . These may be used alone or in combination of two or more. Among these, resin particles are preferable from the viewpoint of easily obtaining flexibility, which is a general mechanical property required for the developing roller.

A ratio of the insulating particles to the total volume of the matrix is preferably 1% by volume or more and 20% by volume or less. When the ratio is 1% by volume or more, a more excellent toner conveying force can be exhibited. Further, when the ratio is 20% by volume or less, it is easy to maintain the conductivity of the coating layer during pressing. The ratio is more preferably 3% by volume or more and 10% by volume or less. The ratio is a value measured by the method described later.

(Additive)
The coating layer according to this aspect can contain various additives other than the binder resin, the conductive particles, and the insulating particles within a range that does not impair the characteristics of the present invention. For example, by adding inorganic compound fine particles such as silica to the coating layer, it is possible to impart reinforcing properties to the coating layer and adjust the dielectric constant of the matrix. In addition, the inorganic compound fine particles as an additive refer to those having an average particle size of less than 1.0 μm. Further, an organic compound additive such as silicone oil may be added to the coating layer for the purpose of improving the performance required of the developing roller, such as improving the toner releasability and reducing the coefficient of dynamic friction.

(Method for forming coating layer)
Although the method for forming the coating layer is not particularly limited, it can be formed, for example, by the following method. A coating liquid for forming a coating layer is prepared which contains the binder resin, the conductive particles, the insulating particles if necessary, and the additives. A substrate or a substrate having a conductive elastic layer formed thereon is dipped in the coating solution and dried to form a coating layer on the substrate.

<Conductive elastic layer>
In the present invention, a conductive elastic layer may be provided between the substrate and the coating layer, if necessary, in order to give the developing roller the elasticity required for the image forming apparatus used. The conductive elastic layer may be either solid or foam. Moreover, the conductive elastic layer may be a single layer or may be composed of a plurality of layers. For example, since the developing roller is in constant pressure contact with the photoreceptor and toner, a conductive elastic layer having low hardness and low compression set is provided in order to reduce mutual damage between these members. can be done. Examples of materials for the conductive elastic layer include natural rubber, isoprene rubber, styrene rubber, butyl rubber, butadiene rubber, fluororubber, urethane rubber, and silicone rubber. These can be used singly or in combination of two or more.

The conductive elastic layer contains a conductive agent, a non-conductive filler, and various additive components necessary for molding, such as a cross-linking agent, a catalyst, and a dispersion accelerator, according to the functions required of the developing roller. good too. As the conductive agent, various conductive metals or their alloys, conductive metal oxides, fine powders of insulating substances coated with these, electronic conductive agents, ion conductive agents, and the like can be used. These conductive agents can be used alone or in combination of two or more in powdery or fibrous form. Among these, carbon black, which is an electron conductive agent, is preferable because it is easy to control conductivity and is economical. Examples of the non-conductive filler include the following. Diatomaceous earth, quartz powder, dry silica, wet silica, titanium oxide, zinc oxide, aluminosilicate, calcium carbonate, zirconium silicate, aluminum silicate, talc, alumina, iron oxide. These may be used alone or in combination of two or more.

The volume resistivity of the conductive elastic layer is preferably 1.0×10 ⁴ to 1.0×10 ¹⁰ Ω·cm. When the volume resistivity of the conductive elastic layer is within this range, fluctuations in the development electric field can be easily suppressed. More preferably, the volume resistivity is 1.0×10 ⁴ to 1.0×10 ⁹ Ω·cm. The volume resistivity of the conductive elastic layer can be controlled by the content of the conductive agent in the conductive elastic layer.

The Asker C hardness of the conductive elastic layer is preferably 10 degrees or more and 80 degrees or less. When the Asker C hardness is 10 degrees or more, it is possible to suppress the compression set due to each member arranged to face the developing roller. In addition, since the Asker C hardness is 80 degrees or less, stress on the toner can be suppressed, and deterioration of image quality due to repeated image formation can be suppressed. The Asker C hardness is a value measured by an Asker rubber hardness tester (manufactured by Kobunshi Keiki Co., Ltd.). The thickness of the conductive elastic layer is preferably 0.1 mm or more and 50.0 mm or less, more preferably 0.5 mm or more and 10.0 mm or less.

As a method for forming the conductive elastic layer, for example, various molding methods such as extrusion molding, press molding, injection molding, liquid injection molding, cast molding, etc. are used to heat and cure at an appropriate temperature and time to form a conductive layer on the substrate. A method of molding the elastic layer can be mentioned. For example, by injecting an uncured conductive elastic layer material into a cylindrical mold in which the substrate is placed and curing it by heating, the conductive elastic layer can be formed on the periphery of the substrate with high accuracy.

[Process Cartridge and Electrophotographic Image Forming Apparatus]
A process cartridge according to this aspect is a process cartridge detachably attached to an image forming apparatus, and has a developing roller according to this aspect. Further, the image forming apparatus according to this aspect has a photoreceptor and the developing roller according to this aspect arranged in contact with the photoreceptor. According to the present invention, it is possible to provide a process cartridge and an electrophotographic image forming apparatus that can stably provide high-quality images under various environments.

FIG. 3 shows an embodiment of the process cartridge according to this aspect. The process cartridge 17 shown in FIG. 3 is detachably attached to the main body of the electrophotographic apparatus, and includes the developing roller 1 according to this embodiment, the developing blade 21, the toner container 20 containing the toner 20a, and the toner supply roller 19. and a developing device 22 having. The process cartridge 17 shown in FIG. 3 is an all-in-one process cartridge integrated with the photoreceptor 18, cleaning blade 26, waste toner container 25, and charging roller 24. As shown in FIG.

An embodiment of an electrophotographic image forming apparatus according to this aspect is shown in FIG. A developing device 22 having a developing roller 1, a toner supply roller 19, a toner container 20 and a developing blade 21 is detachably attached to the electrophotographic image forming apparatus shown in FIG. A process cartridge having a developing device 22, a photoreceptor 18, a cleaning blade 26, a waste toner container 25 and a charging roller 24 is detachably mounted. The photoreceptor 18, the cleaning blade 26, the waste toner container 25 and the charging roller 24 may be arranged in the main body of the image forming apparatus.

The photoreceptor 18 rotates in the direction of the arrow and is uniformly charged by a charging roller 24 for charging the photoreceptor 18. The surface of the photoreceptor 18 is exposed by a laser beam 23, which is an exposure means for writing an electrostatic latent image on the photoreceptor 18. An electrostatic latent image is formed on the The electrostatic latent image is developed by applying toner 20a by a developing device 22 arranged in contact with the photosensitive member 18, and visualized as a toner image. The development is a so-called reversal development that forms a toner image on the exposed portion. The visualized toner image on the photosensitive member 18 is transferred to paper 34, which is a recording medium, by a transfer roller 29, which is a transfer member. A paper 34 is fed into the apparatus via a paper feed roller 35 and a suction roller 36, and is transported between the photoreceptor 18 and the transfer roller 29 by an endless transfer transport belt 32. As shown in FIG. The transfer/conveyor belt 32 is driven by a driven roller 33 , a drive roller 28 and a tension roller 31 . A voltage is applied to the transfer roller 29 and the attracting roller 36 from the bias power supply 30 . The paper 34 onto which the toner image has been transferred is fixed by the fixing device 27 and discharged out of the device to complete the printing operation. On the other hand, untransferred toner remaining on the photoreceptor 18 without being transferred is scraped off by a cleaning blade 26 which is a cleaning member for cleaning the surface of the photoreceptor 18 and stored in a waste toner storage container 25 . The photoreceptor 18 that has been cleaned is subjected to the above-described operations repeatedly.

The developing device 22 includes a toner container 20 containing a toner 20a as a one-component toner, and a developer serving as a toner carrying member located at an opening extending in the longitudinal direction in the toner container 20 and facing the photosensitive member 18. A roller 1 is provided. The developing device 22 develops and visualizes the electrostatic latent image on the photoreceptor 18 . As the developing blade 21, a member in which a rubber elastic body is fixed to a metal plate, a member having a spring property such as a thin plate of SUS or phosphor bronze, or a member in which resin or rubber is laminated on the surface thereof is used. . Further, by providing a potential difference between the developing blade 21 and the developing roller 1, it is possible to control the toner layer on the developing roller 1. For this purpose, the developing blade 21 preferably has conductivity. . A voltage is applied to the developing roller 1 and the developing blade 21 from a bias power source 30, and the voltage applied to the developing blade 21 differs from the voltage applied to the developing roller 1 by about 0V to -300V. preferably.

A developing process in the developing device 22 will be described below. Toner 20a is applied onto the developing roller 1 by a toner supply roller 19 that is rotatably supported. The toner 20 a applied on the developing roller 1 rubs against the developing blade 21 as the developing roller 1 rotates. Here, the toner 20 a on the developing roller 1 is uniformly coated on the developing roller 1 by the bias applied to the developing blade 21 . The developing roller 1 is in contact with the photoreceptor 18 while rotating, and develops the electrostatic latent image formed on the photoreceptor 18 with the toner 20a coated on the developing roller 1, thereby forming an image. As for the structure of the toner supply roller 19, a foam skeleton-like sponge structure or a fur brush structure in which fibers of rayon, polyamide or the like are planted on a substrate are used for supplying the toner 20a to the developing roller 1 and stripping off undeveloped toner. preferred from For example, as the toner supply roller 19, an elastic roller having a substrate provided with polyurethane foam can be used.

[Example 1]
<1. Manufacture of conductive elastic roller>
As a substrate, a stainless steel (SUS304) mandrel having an outer diameter of 6 mm and a length of 270 mm was coated with a primer (trade name: DY35-051, manufactured by Dow Corning Toray Co., Ltd.) and baked. This substrate was placed in a mold, and an addition-type silicone rubber composition mixed with the materials shown in Table 1 below was injected into the cavity formed in the mold. Subsequently, the mold was heated to cure the addition-type silicone rubber composition at a temperature of 150° C. for 15 minutes, and then demolded. After that, the mixture was further heated at a temperature of 180° C. for 1 hour to complete the curing reaction, and a conductive elastic roller 1 having a 2.75 mm-thick conductive elastic layer on the outer circumference of the substrate was manufactured.

<2. Preparation of coating liquid G-1>
Under a nitrogen atmosphere, 100 parts by mass of polybutadiene polyol (trade name: G2000, manufactured by Nippon Soda Co., Ltd.) was gradually added dropwise to 27 parts by mass of polymeric MDI (trade name: Millionate MR200, manufactured by Nippon Polyurethane Industry Co., Ltd.) in a reaction vessel. . At this time, the temperature in the reaction vessel was kept at 65°C. After completion of the dropwise addition, the mixture was allowed to react at 65° C. for 2 hours. The resulting reaction mixture was cooled to room temperature to obtain an isocyanate group-terminated prepolymer B-1 having an isocyanate group content of 4.3% by mass.

55.0 parts by mass of the isocyanate group-terminated prepolymer B-1, 45.0 parts by mass of hydrogenated polyisoprene polyol A-1 (trade name: Epol, manufactured by Idemitsu Kosan Co., Ltd.), and carbon particles C-1 (trade name : ICB0520, manufactured by Nippon Carbon Co., Ltd.) 90.0 parts by mass and 5.0 parts by mass of acrylic particles D-1 (trade name: Techpolymer MBX-15, manufactured by Sekisui Chemical Co., Ltd.) are added to methyl ethyl ketone (MEK). rice field. A mixed liquid 1 was obtained by adjusting the solid content to 40% by mass. 250 parts by mass of the mixed liquid 1 and 200 parts by mass of glass beads having an average particle size of 0.8 mm were placed in a 450 mL glass bottle and dispersed for 30 minutes using a paint shaker (manufactured by Toyo Seiki Co., Ltd.). After that, the glass beads were removed to obtain a coating liquid G-1 for forming a coating layer.

<3. Preparation of Developing Roller>
After the coating liquid G-1 was dipped once on the conductive elastic roller 1, it was air-dried at 23° C. for 30 minutes. Then, it was dried in a hot air circulating dryer set at 160° C. for 1 hour to produce a developing roller X-1 having a coating layer formed on the outer peripheral surface of the conductive elastic roller 1 . The dipping coating immersion time was 9 seconds. The dipping coating pull-up speed was adjusted so that the initial speed was 20 mm/sec and the final speed was 2 mm/sec, and the speed was changed linearly with time between 20 mm/sec and 2 mm/sec.

<4. Physical property evaluation>
(Evaluation 4-1. Current value when not pressed)
Here, in the present invention, a measurement range of 90 μm × 90 μm on the surface of the coating layer was measured using a scanning probe microscope in an environment with a temperature of 23 ° C. and a relative humidity of 50%. , and a spring constant of 42 N/m, the current value measured by scanning in the tapping mode while applying a potential difference of 10 V in the thickness direction of the coating layer is referred to as the current value at the time of non-pressing. A scanning probe microscope (trade name: MFP-3D-Origin, manufactured by Oxford Instruments) was used to measure the current value of the coating layer when not pressed. Measurement conditions are shown below.
Cantilever: ASYELEC-02, manufactured by Olympus Corporation (tip shape: triangular pyramid, tip curvature radius: 25 nm, spring constant: 42 N/m)
Mode: Tapping mode Measurement range: 90 μm x 90 μm
Number of measurement points: 256 points x 256 points Scanning speed: 0.3 Hz
Applied voltage: 10V
Measurement environment: temperature 23°C, relative humidity 50%
The above measurements were carried out at a total of 9 points, ie, 3 points in the axial direction of the coating layer and 3 points in the circumferential direction. Arithmetic mean and standard deviation were determined from the obtained measured values. The results are shown in Table 5 as the "arithmetic mean" and "standard deviation" of the non-pressing current values.

(Evaluation 4-2. Conductive point density during pressing)
A scanning probe microscope was used to measure the conductive point density on the surface of the coating layer during pressing. Specifically, MFP-3D-Origin, manufactured by Oxford Instruments Co., Ltd. was used. Measurement conditions are shown below.
Cantilever: ASYELEC-02, manufactured by Olympus Corporation (tip shape: triangular pyramid, tip curvature radius: 25 nm, spring constant: 42 N/m)
Mode: Contact mode Contact pressure: 2.0 μN (impulse: 77 nm/V)
Measurement range: 90 μm×90 μm
Number of measurement points: 256 points x 256 points Scanning speed: 0.3 Hz
Applied voltage: 10V
Measurement environment: temperature 23°C, relative humidity 50%

A current image of the measurement range was obtained by the above measurement. In the case of the developing roller according to this aspect, the main measurement reveals conductivity at the positions of the conductive particles, and a large current value is obtained. Therefore, the current image is obtained with the positions of the conductive particles as island-shaped independent regions. Here, the number of independent regions exhibiting conductivity in the measurement range was counted, with the regions where the current value was 1 μA or more in the measurement being regarded as regions exhibiting conductivity. From the number of independent regions and the area of the measurement range, the conductive point density during pressing was calculated as the number of independent regions/measurement range. This measurement was performed at a total of 9 points, ie, 3 points in the axial direction of the coating layer and 3 points in the circumferential direction. From the obtained measured values, the arithmetic mean value of the density of conductive points during pressing was obtained. The results are shown in Table 5 as "conducting point density during pressing".

(Evaluation 4-3. Local potential difference)
The surface of the coating layer was charged using a corona discharge device (trade name: DRA-2000L, manufactured by QEA) in an environment of 23° C. temperature and 50% relative humidity. The device is equipped with a head in which a corona discharger and a probe of a surface potential meter are integrated, and the head can be moved while performing corona discharge.
Specifically, a potential difference of +8 kV is applied to the surface of the coating layer, the distance between the surface of the coating layer and the corona charger is set to 1 mm, and the developing roller is scanned in the longitudinal direction at a speed of 400 mm/sec. electrified.
Then, 1 minute after the charging, a range of 99 μm×99 μm on the surface of the coating layer was measured in an environment with a temperature of 23° C. and a relative humidity of 50% using a high spatial resolution surface potential measuring device. The potential was measured while scanning with a distance of 5 μm from the cantilever of the high spatial resolution surface potential measuring device. Here, the standard deviation of the obtained potentials is called the local potential difference.
For the local potential difference of the coating layer, the potential of the surface of the developing roller charged by corona discharge was measured with an electrostatic force microscope. The measurement environment was a temperature of 23° C. and a relative humidity of 50%.
As a specific operating method, first, a master made of stainless steel (SUS304) having the same outer diameter as the developing roller was placed in the corona discharge device, and this master was short-circuited to the ground. Then, the distance between the master surface and the probe of the surface electrometer was adjusted to 1.0 mm, and the surface electrometer was calibrated to zero. After this calibration, the master was removed and a developing roller to be charged was placed in the apparatus. The developing roller was charged with the bias setting of the corona discharger set to +8 kV, the conductive substrate of the developing roller set to GND, and the moving speed of the scanner set to 400 mm/sec.

Subsequently, the potential of the charged developing roller was measured using a high spatial resolution surface potential measuring device (MODEL 1100TN, manufactured by Trek Japan Co., Ltd.). A commercially available high-precision XY stage was used for scanning the developing roller. Measurement conditions are shown below.
Measurement environment: temperature 23°C, relative humidity 50%;
Time from corona discharge to start of measurement: 1 min;
Cantilever: Product name: Model 1100TNC-NPR, manufactured by Trek Japan;
Gap between coating layer surface and cantilever tip: 5 μm;
Measurement range: 99 μm×99 μm;
Measurement interval: 3 μm×3 μm.
The above measurements were carried out at a total of 9 points, ie, 3 points in the axial direction of the coating layer and 3 points in the circumferential direction. The arithmetic mean value and standard deviation of the surface potential were obtained from the obtained measured values. The results are shown in Table 5 as "arithmetic mean" and "standard deviation" of surface potential.

(Evaluation 4-4. Roller volume resistivity during pressing)
The volume resistivity of the developing roller when pressed was measured using the apparatus shown in FIG. The measurement was performed in an environment of 23° C. temperature and 50% relative humidity.
A stainless steel roller 37 having a diameter of 30 mm and a width of 10 mm is placed between the circumferential surface of the stainless steel roller 37 and the developing roller 1 so that the axial direction of the stainless steel roller 37 and the axial direction of the developing roller 1 are perpendicular to each other. The circumferential surface of the roller was made to face.
Next, the stainless steel roller 37 was brought into contact with a load 38 that applied a pressure of 50 kPa to the surface of the developing roller 1 .
Next, a potential difference of 10 V was applied from the high voltage power supply 39 to the conductive substrate 2 .
Next, the stainless steel 37 roller was rolled in the axial direction of the developing roller at a speed of 50 mm/sec by a driving means (not shown) over a range excluding 5 mm at both ends in the axial direction of the developing roller.
At this time, the potential difference between the stainless steel roller 37 and the conductive substrate 2 was measured by the recorder 41 at intervals of 1000 Hz. A current value was obtained from the measured potential difference and the electrical resistance of the resistor 40 .
The above measurements were performed at 36 points in the circumferential direction of the developing roller.
The volume resistivity is calculated from the measured current value, the contact area when the pressure applied from the stainless steel roller 37 to the surface of the developing roller 1 is 0.10 MPa, and the separately measured thickness of the developing roller. and calculated the arithmetic mean and standard deviation.
The calculation results are shown in Table 5 as "arithmetic mean value" and "standard deviation" of the roller volume resistivity during pressing.

Here, the load at which the pressure applied to the surface of the developing roller becomes 0.10 MPa and the contact area at that time were obtained as follows. A prescale (manufactured by Fuji Film Co., Ltd.; for fine pressure (4LW)) was sandwiched between the stainless steel roller 37 and the developing roller 1, and a weight was placed on the stainless steel roller 37 to load the developing roller 1. 38 was loaded. Next, the area of contact was determined using an optical microscope from the red-colored region of the prescale. From the load and contact area at this time, the pressure applied from the stainless steel roller 37 to the surface of the developing roller 1 was calculated as load/contact area. This operation was performed while changing the weight of the weight, and a load was obtained at which the pressure applied from the stainless steel roller 37 to the surface of the developing roller 1 was 0.10 MPa.

(Evaluation 4-5. Thickness of coating layer)
Cross sections of the coating layer at 3 points in the axial direction and 3 points in the circumferential direction (9 points in total) were observed with an optical microscope or an electron microscope. The layer thickness of the coating layer was measured at 10 random points at each measurement point. The arithmetic mean value of the obtained 90 points in total was used as the layer thickness of the coating layer. The results are shown in Table 6 as "layer thickness".

(Evaluation 4-6. Nanoindenter hardness)
The nanoindenter hardness on the matrix and the conductive particles was measured using an ultra-micro hardness tester (trade name: PICOPDENTOR HM-500, manufactured by Helmut Fischer). Measurement conditions are shown below.
Measurement indenter: Vickers indenter, face angle 136, Young's modulus 1140, Poisson's ratio 0.07;
Indenter material: diamond;
Measurement environment: temperature 23°C, relative humidity 50%;
Loading speed: 0.10 mN/10 seconds.

In this evaluation, the Martens hardness calculated by the following formula (1) was taken as the nanoindenter hardness. In the measurement on the matrix, the distance between the conductive particles was measured, and in the measurement on the conductive particles, the peaks of the protrusions derived from the conductive particles were measured. For each of the matrix and the conductive particles, measurements were taken at 3 points in the axial direction×3 points in the circumferential direction, totaling 9 points, and an average value was obtained. Martens hardness is obtained by contacting the tip of the indenter, applying the load F at the speed described in the above conditions, determining the indentation depth h at the time when the load F reaches 0.10 mN, and calculating the following formula (1 ). Table 6 shows the nanoindenter hardness of the matrix as the matrix "hardness" and the nanoindenter hardness on the conductive particles as the "hardness" of the conductive particles.
Formula (1)
Nanoindenter hardness (N/mm ² ) = F (N)/surface area of indenter under test load (mm ² ) = F/(26.43 x h ² )
F: Load (N)
h: Indentation depth of indenter (mm)

(Evaluation 4-7. Mode of spherical volume equivalent diameter of conductive particles)
The mode of the spherical volume equivalent diameter of the conductive particles and the insulating particles was measured using an FIB-SEM (trade name: NVision 40, manufactured by Carl Zeiss Microscopy Co., Ltd.).
A specific measurement method is shown below. A blade of a cutter is applied to the developing roller, and sections are cut with a length of 5 mm each in the x-axis direction (longitudinal direction of the roller) and the y-axis direction (the tangential direction of the circular cross section in the cross section of the roller perpendicular to the x axis). cut out.
The cut section was observed from the z direction (diameter direction in the cross section of the roller perpendicular to the x axis) using an FIB-SEM apparatus at an acceleration voltage of 10 kV and a magnification of 1000 times.
Next, the film was sliced at intervals of 100 nm in the z direction, and a cross-sectional image of the coating layer from the surface to the entire z direction was taken. The obtained cross-sectional image was binarized by the Otsu method using analysis software, constructed in three dimensions, and the volume of the conductive particles was calculated.
From the volume of the obtained conductive particles, the equivalent sphere volume diameter ((3×volume of conductive particles/4×π) ^1/3 ) was calculated. This was carried out at a total of 9 or more locations, ie, 3 locations in the axial direction of the developing roller and 3 locations in the circumferential direction, to obtain the volume of 500 conductive particles and the volume-equivalent diameter of the sphere.
From the obtained results, create a histogram with the horizontal axis representing the sphere volume equivalent diameter at intervals of 0.1 μm and the vertical axis representing the volume ratio of the conductive particles contained in each sphere volume equivalent diameter interval to the total conductive particle volume. The volume-equivalent sphere diameter with the largest volume ratio was taken as the mode of the volume-equivalent sphere diameter of the conductive particles.
For example, when the volume-equivalent diameter of the sphere with the largest volume ratio is included in the range of 7.1 μm or more and less than 7.2 μm, the mode is set to 7.1 μm. The results are shown in Table 6 as "particle size".

(Evaluation 4-8. Content of conductive particles and insulating particles)
The content (% by volume) of the conductive particles and the insulating particles was measured using an FIB-SEM (trade name: NVision40, manufactured by Carl Zeiss Microscopy Co., Ltd.).
A specific measurement method is shown below. A blade of a cutter is applied to the developing roller, and sections are cut with a length of 5 mm each in the x-axis direction (longitudinal direction of the roller) and the y-axis direction (the tangential direction of the circular cross section in the cross section of the roller perpendicular to the x axis). cut out.
The cut section was observed from the x direction using an FIB-SEM apparatus at an acceleration voltage of 10 kV and a magnification of 1000 times. Next, it was sliced at intervals of 100 nm in the z direction, and a total of 300 cross-sectional images were taken from the surface to a depth of 30 μm.
The obtained cross-sectional images were binarized by the Otsu method using analysis software, constructed in three dimensions, and the volumes of the coating layer, the conductive particles, and the insulating particles were calculated. This operation was performed at a total of 9 locations, ie, 3 locations in the axial direction of the developing roller and 3 locations in the circumferential direction.
The arithmetic mean value of the volume of the conductive particles with respect to the volume of the coating layer at each location, and the arithmetic mean value of the volume of the insulating particles with respect to the volume of the coating layer, respectively, the conductive particles and the coating layer with respect to the total volume of the coating layer The ratio (% by volume) occupied by the insulating particles with respect to the total volume. The results are shown in Table 6 as "content".

(Evaluation 4-9. Overlap of conductive particles)
The overlapping of the conductive particles in the coating layer thickness direction was measured using an FIB-SEM (trade name: NVision40, manufactured by Carl Zeiss Microscopy Co., Ltd.).
A specific measurement method is shown below. A blade of a cutter is applied to the developing roller, and sections are cut with a length of 5 mm each in the x-axis direction (longitudinal direction of the roller) and the y-axis direction (the tangential direction of the circular cross section in the cross section of the roller perpendicular to the x axis). cut out.
The cut section was observed from the x direction using an FIB-SEM apparatus at an acceleration voltage of 10 kV and a magnification of 1000 times. Next, the film was sliced at intervals of 100 nm in the z direction, and a cross-sectional image of the coating layer from the surface to the entire z direction was taken. The obtained cross-sectional images were binarized by the Otsu method using analysis software, and three-dimensionally constructed.
From the obtained three-dimensional image, the number of conductive particles overlapping in the z direction was counted at intervals of 1 μm×1 μm on the xy plane, and the arithmetic mean value was obtained. The results are shown in Table 6 as "Overlap".

(Evaluation 4-10. Potential Decay Time Constant of Matrix)
The time constant of the potential decay of the matrix was calculated from the decay transition obtained by measuring the decay transition of the potential of the matrix surface after electrification by corona discharge with an electrostatic force microscope. The potential of the matrix was the surface potential at positions between the conductive particles on the surface of the developing roller. The measurement environment was a temperature of 23° C. and a relative humidity of 50%.

A corona discharge device (trade name: DRA-2000L, trade name, manufactured by QEA) was used for the measurement. The device is equipped with a head in which a corona discharger and a probe of a surface potential meter are integrated, and the head can be moved while performing corona discharge.
A master made of stainless steel (SUS304) having the same outer diameter as the developing roller was installed in the apparatus, and this master was short-circuited to the ground. Then, the distance between the master surface and the probe of the surface electrometer was adjusted to 1.0 mm, and the surface electrometer was calibrated to zero.
After this calibration, the master was removed and a developing roller to be charged was placed in the DRA-2000L. The developing roller was charged with the bias setting of the corona discharger set to +8 kV, the conductive substrate of the developing roller set to GND, and the moving speed of the scanner set to 400 mm/sec.

Subsequently, the potential of the matrix surface was measured using an electrostatic force microscope (trade name: MODEL 1100TN, manufactured by Trek Japan). A commercially available high-precision XY stage was used for scanning the developing roller. Measurement conditions are shown below.
Measurement environment: temperature 23°C, relative humidity 50%;
Time from corona discharge to start of measurement: 1 min;
Cantilever: EFM cantilever with light shield;
Gap between coating layer surface and cantilever tip: 5 μm;
Measurement time: 100 sec;
Measurement interval: 100 Hz.

A time constant was calculated by fitting with the following formula (2) by the method of least squares from the transition of decay of the obtained surface potential.
Formula (2)
V=V0×exp((−t/τ) ^1/2 )
V: measured potential, V0: initial potential, t: elapsed time from corona discharge to measurement, τ: time constant.

This measurement was performed at a total of 9 points, ie, 3 points in the axial direction of the developing roller and 3 points in the circumferential direction.
An arithmetic mean value was calculated from the obtained time constants and used as the potential attenuation time constant of the developing roller. The results are shown in Table 6 as "potential decay time constant".

(Evaluation 4-11. Roughness)
A laser microscope (trade name: VK-8700, manufactured by Keyence Corporation) was equipped with an objective lens with a magnification of 50 times to observe the surface of the developing roller. Next, tilt correction of the obtained observed image was performed. Tilt correction was performed in the quadric surface correction (automatic) mode. After that, the surface roughness was measured. The surface roughness was determined in accordance with JIS B0601:2001 over the entire measured area. This measurement was performed at a total of 9 points (3 points in the axial direction of the developing roller×3 points in the circumferential direction), and the average value was taken as the surface roughness of the developing roller. The results are shown in Table 6 as "roughness".

(Evaluation 4-12. Specific circumference length of conductive particles)
A FIB-SEM (trade name: NVision40, manufactured by Carl Zeiss Microscopy Co., Ltd.) was used to measure the specific perimeter of the conductive particles.
A specific measurement method is shown below. A blade of a cutter is applied to the developing roller, and sections are cut with a length of 5 mm each in the x-axis direction (longitudinal direction of the roller) and the y-axis direction (the tangential direction of the circular cross section in the cross section of the roller perpendicular to the x axis). cut out. The cut section was observed from the z direction (diameter direction in the cross section of the roller perpendicular to the x axis) using an FIB-SEM apparatus at an acceleration voltage of 10 kV and a magnification of 1000 times. Next, the film was sliced at intervals of 100 nm in the z direction, and a cross-sectional image of the coating layer from the surface to the entire z direction was taken. Of the obtained cross-sectional images, the cross-sectional image at the center position of the coating layer in the z direction was binarized by the Otsu method using analysis software. From this binarized cross-sectional image, the cross-sectional area and perimeter of each conductive particle were measured using an automatic image processing analyzer (Luzex, manufactured by Nireco Corporation). From the obtained cross-sectional area of the conductive particles, the circumference corresponding to the circular area of the conductive particles (2×π×(4×cross-sectional area of the conductive particles/π) ^1/2 ) was calculated. A specific perimeter (perimeter/equivalent circle diameter) was calculated from the obtained perimeter and equivalent circle diameter. This was performed for 500 conductive particles, and the arithmetic mean value was taken as the specific circumference of the conductive particles. Table 6 shows the results.

<5. Image evaluation>
In a normal temperature and normal humidity environment with a temperature of 23°C and a relative humidity of 50%, a high temperature and high humidity environment (temperature of 30°C and a relative humidity of 80%), and a low temperature and low humidity environment (a temperature of 15°C and a relative humidity of 10%). The following image evaluation was performed. First, in order to reduce the torque of the electrophotographic member, the gear of the toner supply roller was removed from the process cartridge (trade name: HP 410X High Yield Magenta Original LaserJet Toner Cartridge (CF413X), manufactured by Hewlett-Packard). Originally, the toner supply roller rotates in the opposite direction to the developing roller during operation of the process cartridge. However, by removing the gear, the toner supply roller is driven to rotate relative to the developing roller. As a result, while the torque is low, the amount of toner supplied to the developing roller is reduced. Next, the produced developing roller was incorporated into the process cartridge, and the process cartridge was loaded into an image forming apparatus, a laser beam printer (trade name: Color Laser Jet Pro M452dw, manufactured by Hewlett-Packard Co.). Next, this laser beam printer was aged for 24 to 48 hours in an image evaluation environment.

(Image evaluation 5-1. Evaluation of toner conveying force)
After the aging, under the same environment, a solid black image (100% density) was output on one sheet of A4 paper. The image density of the obtained solid black image was measured using a spectral densitometer (trade name: 508, manufactured by Xrite) to determine the density difference between the leading edge and the trailing edge of the image in the conveying direction of A4 paper. The evaluation criteria for the image density difference are as follows. The results are shown in Table 7 as "toner conveying force".
Rank A: The image density difference is less than 0.05, and the toner conveying power is very high.
Rank B: The image density difference is 0.05 or more and less than 0.10, and the toner conveying power is high.
Rank C: The image density difference is 0.10 or more and less than 0.20, and the toner conveying force is within the allowable range.
Rank D: The image density difference is 0.20 or more, and the toner conveying power is low.

(Image Evaluation 5-2. Evaluation of Image Density Change)
After the aging, under the same environment, a halftone (density 50%) image was printed on an A4 sheet. The image density of the resulting halftone image was measured using the spectral densitometer. Next, after outputting 1000 sheets of A4 solid white (density 0%) image, one sheet of halftone (50% density) image was output quickly. The image density of the obtained halftone image was similarly measured, and the density difference before and after outputting 1000 sheets was obtained. The evaluation criteria for the image density difference are as follows. The results are shown in Table 7 as "image density change".
Rank A: The image density difference is less than 0.05, and the image density change is very small.
Rank B: The image density difference is 0.05 or more and less than 0.10, and the image density change is small.
Rank C: The image density difference is 0.10 or more and less than 0.20, and the image density change is within the allowable range.
Rank D: The image density difference is 0.20 or more, and the image density change is large.

[Examples 2 to 50, Comparative Examples 1 to 10]
<1. Manufacture of conductive elastic roller>
As a substrate, a stainless steel (SUS304) mandrel having an outer diameter of 6 mm and a length of 260 mm was coated with a primer (trade name: DY35-051, manufactured by Dow Corning Toray Co., Ltd.) and baked. An unvulcanized rubber composition was prepared by kneading the materials shown in Table 2 below. Next, a crosshead extruder having a substrate feeding mechanism and an unvulcanized rubber composition discharging mechanism was prepared. Second, the transport speed of the substrate was adjusted to 60 mm/sec. Under these conditions, the unvulcanized rubber composition was supplied from the extruder, and the outer periphery of the substrate was covered with the unvulcanized rubber composition as an elastic layer in the crosshead to obtain an unvulcanized rubber roller. Next, the unvulcanized rubber roller was placed in a hot air vulcanizing furnace at 170° C. and heated for 15 minutes. After that, it is polished with a rotary polishing machine (trade name: LEO-600-F4L-BME, manufactured by Minakuchi Seisakusho Co., Ltd.) using a grindstone of GC80, and a conductive elastic layer having a thickness of 2.0 mm is formed on the outer circumference of the mandrel. A conductive elastic roller 2 having

<2. Preparation of Coating Liquids G-2 to G-58>
In Example 1, the polyol used in preparing the isocyanate group-terminated prepolymer B-1 was changed to the polyol shown in Table 3. Otherwise, isocyanate group-terminated prepolymers B-2 to B-5 having an isocyanate group content of 4.3 mol % were prepared in the same manner as isocyanate group-terminated prepolymer B-1. Further, coating liquids G-2 to G-58 were prepared in the same manner as coating liquid G-1, except that the composition was changed to that shown in Table 3 and the solid content was adjusted to the target coating layer thickness. was prepared. Specific material names of polyol A, isocyanate group-terminated prepolymer B, conductive particles C, and insulating particles D described in Table 3 are shown in Table 4. In addition, "parts" in Table 3 indicate "mass parts".

<3. Preparation of Developing Roller>
Developing rollers X-2 to X-49 and Y-2 to Y-9 were produced in the same manner as in Example 1, except that the coating solution used for forming the coating layer was changed as shown in Table 3. A developing roller X-50 was manufactured in the same manner as in Example 1, except that the conductive elastic roller 1 was changed to the conductive elastic roller 2.

In addition, the surface of the roller manufactured in the same manner as in Example 1 except that the coating liquid used for forming the coating layer was changed to G-50 was treated with a rubber roll mirror finishing machine (trade name: SZC, manufactured by Minakuchi Seisakusho Co., Ltd.). A portion of the insulating particles was exposed to produce a developing roller Y-1.

In the same manner as the conductive elastic roller 1, except that the carbon black of the conductive elastic roller 1 was changed to carbon particles C-1 (trade name: ICB0520, manufactured by Nippon Carbon Co., Ltd.), the outer circumference of the mandrel was made thick. A conductive elastic roller 3 (developing roller Y-10) having a coating layer thickness of 2.0 mm was produced.

Table 3 shows combinations of the conductive elastic rollers of the developing rollers X-2 to X-50 and Y-1 to Y-10 and the coating liquid. Developing rollers X-2 to X50 and Y-1 to Y-10 were evaluated in the same manner as in Example 1. The results are shown in Tables 5-7. In Y-1 and Y-3, the average primary particle size of carbon black, which is the conductive particles, is small, the nanoindenter hardness of the matrix, the nanoindenter hardness on the conductive particles, and the matrix Since it was difficult to measure the potential decay time constant of the matrix, the evaluation was performed without distinguishing between the matrix and the conductive particles. The results are shown in Table 6 as matrix hardness and potential decay time constant.

As shown in Table 7, the developing rollers of Examples 1 to 50, which satisfy the configuration of the present invention, were able to achieve both suppression of image density change and high toner conveying power at a high level.

Reference Signs List 1 developing roller 2 substrate 3 coating layer 4 conductive elastic layer 5 matrix 6 conductive particles 7 insulating particles

Claims (7)

A developing roller having a conductive substrate and a coating layer on the conductive substrate,
The coating layer has a matrix containing a binder resin and conductive particles dispersed in the matrix,
A 90 μm × 90 μm square measurement area on the outer surface of the coating layer was measured under an environment of a temperature of 23 ° C. and a relative humidity of 50% using a scanning probe microscope with a triangular pyramid tip, a tip curvature radius of 25 nm, and a spring constant of is 42 N/m, and the current value is measured by scanning in a tapping mode while applying a potential difference of 10 V in the thickness direction of the coating layer, the arithmetic average value of the current value is 300 pA or less. , the standard deviation of the current value is 0.1 times or less of the current value,
The outer surface of the coating layer was subjected to a temperature of 23° C. and a relative humidity of 50% using a corona charger, and a potential difference of +8 kV was applied to the coating layer surface. 1 mm, and electrified while scanning at a speed of 400 mm/sec in the longitudinal direction of the developing roller. In an environment with a relative humidity of 50%, the potential is measured while the distance between the coating layer surface and the cantilever of the surface potential measuring device is 5 μm, and the standard deviation of the obtained potential is 3.0 V or more. hand,
A stainless steel roller having a diameter of 30 mm and a width of 10 mm was placed in an environment with a temperature of 23° C. and a relative humidity of 50% so that the axial direction of the stainless steel roller and the axial direction of the developing roller were perpendicular to each other. The circumferential surface of the manufacturing roller and the circumferential surface of the developing roller are opposed to each other, and the stainless steel roller is brought into contact with the developing roller surface with a load of 0.10 MPa. A potential difference of 10 V was applied between the roller and the conductive substrate, and the stainless steel roller and the conductive substrate were separated while rolling the stainless steel roller in the axial direction of the developing roller at a speed of 50 mm/sec. When the current value is measured at 36 points in the circumferential direction of the developing roller, the arithmetic mean value of the volume resistivity obtained from the measured current value is 10 ¹⁰ Ω cm or less, A developing roller, wherein the standard deviation is 1 or more times the arithmetic mean value of the volume resistivity. The layer thickness of the coating layer is 3.0 μm or more and 30 μm or less,
The mode of the spherical volume equivalent diameter of the conductive particles is 3.0 μm or more and 20 μm or less,
The arithmetic average value of the number of the conductive particles overlapping in the thickness direction of the coating layer is 3 or less,
The ratio of the conductive particles to the total volume of the coating layer is 20% by volume or more and 45% by volume or less,
Under an environment of a temperature of 23° C. and a relative humidity of 50%, the potential decay time constant of the matrix is 1.0 min or more,
In an environment with a temperature of 23° C. and a relative humidity of 50%, the nanoindenter hardness of the matrix on the surface of the coating layer is 0.1 N/mm ² or more and 3.0 N/mm ² or less,
The nanoindenter hardness on the conductive particles is 1.0 N/mm ² or more and 10.0 N/mm ² or less,
the nanoindenter hardness on the conductive particles is greater than the nanoindenter hardness of the matrix;
2. The developing roller of claim 1. 3. The conductive particles according to claim 1 or 2, wherein the conductive particles are at least one selected from the group consisting of metal particles, particles having conductive fine particles attached to their surfaces, resin particles encapsulating conductive fine particles, and carbon particles. developer roller. 4. The developing roller according to any one of claims 1 to 3, wherein the conductive particles are carbon particles, and the conductive particles have a specific circumferential length of 1.1 or less. The binder resin is
one or both of the structures represented by the following formulas (1) and (2);
one or both of the structures represented by the following formulas (3) and (4);
The developing roller according to any one of claims 1 to 4, having a structure represented by the following formula (5):

(In formula (5), l represents an integer of 1 or more.). A process cartridge detachably attached to a main body of an electrophotographic apparatus, comprising the developing roller according to any one of claims 1 to 5. An electrophotographic image forming apparatus comprising a photoreceptor and a developing roller for supplying developer to an electrostatic latent image formed on the photoreceptor, wherein the developing roller is any one of claims 1 to 5. 2. An electrophotographic image forming apparatus characterized by being the developing roller according to item 1 or 2.

Images